I'm having difficulty with difficulty , so here's a few more questions:

While looking at various builds in the forum, I often see DC in the description. According to the wiki Glossary as well as the forum's DDO Acronyms and Slang Terminology, DC is either disconnect or Difficulty Check/Class. I'm having trouble seeing how either meaning applies to a build. Is there another meaning for DC in this case?

Next, regarding quest difficulty, the wiki says that Normal and lower difficulty is okay for soloing due to scaling. However, while Hard and Elite do mention scaling, they do not mention solo which seems to imply that Hard and higher difficulty should not be attempted solo. Am I interpreting that correctly, or are Hard difficulty quests doable solo? If they are doable solo, is that only using a higher level character, with hirelings, or any other requirements?

Thanks!

From Difficulty:
Normal

Dungeon Scaling is in full standard effect.
Enemy misses become Grazing Hits on raw die rolls of 17-19.
Rest Shrines can be used every 15 minutes.
Most normal difficulty dungeons are most evenly balanced against a party of four players. However most quests are also designed to be soloable on normal as well due to scaling. If it's a raid, 12 players are still recommended, but often not required.
Normal difficulty is intended to be the default choice for the large majority of players looking for a balanced experience.
Monster Damage Reduction, at their best, block only 50% of your damage instead of their true value
Hard

Dungeon Scaling is in effect, but has less of an impact than Normal.
Favor is 2 × Normal.
Main XP is roughly 1.05 to 1.08 × Normal.
There may be more and/or larger encounters than Normal.
Enemies are always a higher CR, and have far higher statistics designed to challenge more prepared parties.
Enemy spell casters often have more and higher level spells.
Monster Damage Reduction, at their best, block only 75% of your damage instead of their true value.
For example: If your attack deals 16 damage, but the monster has DR 15/-, your attack still deals 4 damage. You can see it better against the DR 100 monsters: ghostly skeletons in Delera's and gargoyles in Stone Form.
Enemies can upgrade to a Tier 1 Monster Champion.
The quest's level is increased by 1 solely for purposes of generating better chest loot and comparing against the party's level for XP adjustment. Rewards from the quest's giver are unaffected.
Traps are greatly increased in difficulty, in terms of damage dealt, save DC and skill DC needed to disable them. They are intended to challenge decently-geared rogues of appropriate level.
Hidden doors and Lock DCs sometimes scale up a few points.
Enemy misses become Grazing Hits on raw die rolls of 15-19.
Rest Shrines can only be used once. Some quests have fewer shrines when compared to Normal.
Hard is intended for full, well-balanced groups of 6 players, or 12 if it's a raid.
Free to play and premium players cannot open a quest on hard unless they have already completed it on Normal or higher difficulty, or they underwent True Reincarnation at least once. They can use Hard Difficulty Quest Unlock Token from the DDO Store to bypass this limitation.